SU1008621A1 - Level indicator - Google Patents

Abstract

LEVELNER on avt.SV. No. 900120, characterized in that, in order to increase the accuracy of the WH Jr HIZ measurements in the low-level region, c. it is entered sequentially connected dummy frequency shaping circuit and additional switch, connected between the input frequency shaping circuit and the inputs of two main switches, and the circuit is allocated to the level of the correction circuit connected by one input to the input of the overflow indication circuit, the other input to the control signal generation circuit, and the output to the additional switch, also connected to the output of the sensor. CJ hum HULG / G Urod it ceiu (iHi

Description

The invention relates to a measurement technique and can be used in cryogenic, naphtochemical and other industries to measure the level of dielectric media. According to the main author. St. No. 900120 is known for a level gauge containing a sensor, a control signal generation circuit, two switching circuits, a frequency shaping circuit, two logic circuits, a coefficient memory block, two reversible counters, an overflow fixation circuit, a register level, a counter, and a section register l A disadvantage of the known level gauge is a large error in measuring low environmental levels. In the process of measuring the level from a multisection sensor, the computational converter implements a 2-loil l compensation algorithm. ),. (n.e) current value of the frequency of the working section of the sensor; .E) the current value of the frequency of the adjustment section of the sensor; f € is the initial value of 0-1 02 nor the frequencies f and f „. The value of frequency f -2 always corresponds to the frequency of the fully filled sensor section, which is due to the compensation properties of the algorithm. When polling the first section of the sensor in the gage, the frequency f comes from the first section, and f2 from the correction loop of the sensor (Fig. 1). If the level of the controlled medium in the first section turns out to be lower than h c (fig. Then the correction circuit will be partially filled and its frequency in this case% creative will differ from the frequency g 2 kk. Of the completely filled correction circuit by the value Af 2 2k рес resIlT 2 kk, which will lead to an error dN level measurement in the first section of the sensor. The magnitude of the error in measuring the level within the corrective length of the correction wave can reach 10-20%. The purpose of the invention is to improve the measurement accuracy in the low-level region. by introducing a dummy frequency shaping circuit and an additional switch, connected between the input of the shaping circuit and the inputs of two main switches, and a leveling circuit of the correction circuit, connected by one input to the input of the overflow sign circuit, another input to the circuit generating control signals, and the output to an additional switch, also connected to the output of the sensor. FIG. 1 shows a structural diagram of the level gauge; FIG. 2 is one of the embodiments of the control signal generation circuit. The gauge contains sensor 1, block 2 of the fo-i and fo2 frequency memory circuit 3 generating fictitious frequency 2 fc control signal generation circuit 4, switching circuits 5-7, logic gates 8 and 9, coefficient memory block 10, reversible counters 11 and 12, a trigger 13, a register 14. a level, a circuit 15 for allocating a level of the correction loop, a circuit 16 for overflow, a counter 17 and a register 18 for the number of sections. The measuring f channel of the multisection sensor 1 is connected to the switching circuits 5 and 6, and the compensation channel f2 is connected to the input of the switching circuit 7. The outputs of the switching circuit b are connected to the counting inputs of the reversible counter 12, and the switching circuits 5 are connected to the inputs of logic circuits 8 and 9, respectively, connected by their outputs with the summing and subtracting inputs of the reversing counter 11. The inputs foiH 2 are connected to the inputs 5 and b frequency shaping and bus Q of the control signal generation circuit 4, and to other inputs of the switching circuit 7, the output f 2ms of the dummy frequency shaping circuit 3 and the output bus of the circuit 15 for correcting the level of the correction circuit. Outputs (Up to, Qg and Q of circuit 4 are connected to memory block 10, outputs (of which are connected to code inputs of reversible counter 11, connected by their outputs with corresponding code inputs of second reversible counter (PC) 12, level register 14, circuit 15 the selection of the level of the critical contour and overflow circuit 16. PC 12 is connected to trigger 13, a single output of which is connected to the input of switching circuit 6 and the inputs of logic circuits 8 and 9. One output of overflow circuit 16 is connected to counter 17 connected to register 18 sections and the second to the entrances of setups of registers 14 and 18. Outputs q, - circuits 4 are connected respectively to a reversible counter 11 and trigger 13, a reversible counter 12, a counter 17, a 16-overflow circuit and a level correction circuit 15 of the correct level. The outputs qf and circuit 4 are connected to Level sensor 1 to ensure its synchronous operation with the secondary transducer. The output of the level gauge is removed from the register of 18 sections, which stores the number of completely filled sections and register 14 for storing the level code inside the current section. The basis of the sensor action is a cyclical interrogation of the sensor sections in time, starting from the first, with the formation of each section of the NH level code N for it during the time and the formation of the signal V 1 if the level is in the i-section H,. or Chao.gr. i -, where Hj., p is the level of a fully populated i-section.

In the proposed device introduced a double poll of the first section of the sensor. In the first of them, the frequency f2 jiK is used as the frequency f2 of the correction section of the sensor. On the basis of the obtained level value, a conclusion is made whether the correction loop is full or partial. If the level is less than h UROEN.:. a completely filled correction loop, then the correction loop is filled. partially, and therefore its frequency ® can be used to measure the level of the first section of the sensor, therefore during the second survey it is necessary to use the frequency 2fc. If the first survey yields the value of the level in the first section greater than h, then at the second survey the first section of the sensor as frequency f2 is used by 2. Note herewith that the result of the first poll is not displayed anywhere and is used by the computational converter only for switching frequencies f for the first section.

If the level of the secondary transducer is switched to the second section when polling the first section H °, the sensor In this case, the frequencies are switched according to the following law: f is removed from the second section, f2 of the first section. Further, when polling the following sections, the frequency f is removed from the i-section and f2 from the Vi-1) section.

During the entire sensor polling cycle, the number of completely filled NceKu, sections is determined. and level N (inside the current section. The value of the level Kc. in each section is sequenced at the output of the reversing counter 12.

When calculating the code level

dependence 2 is realized

J01 1

(one)

2:

with its simultaneous linearization, carried out by approximating the function

 (2;

0

second degree polynomial

P2t2) o (2-2 + a) Z + olo. (3)

5 Consider the operation of the device in

during the survey cycle polling multisection sensor T:

T f-Tj; . (4) where T is the polling time of one section

K - the number of sections.

0 For synchronous operation of the device at the beginning of a T.jv cycle. The counter 17 and the section counter in the multisection sensor 1 are reset by means of signals c, and c, the frequencies f and ± 2 corresponding to the first section are connected to the input of the secondary converter.

During the time T (, the formation of the corresponding

 The code of the level NH H in six cycles T. During this time, the dependence (1) and the polynomial (3) are implemented jointly. The control of the sequence of calculations is performed by

5 by circuit 4 having the classical structure of a synchronous type control device.

One of the options for building a control signal generation scheme

0 is shown in FIG. 2

The device includes a clock frequency generator 19. a clock pulse frequency counter F with a conversion factor of six, de 5 an encoder 21 of Q signals necessary for sampling the coefficients codes of the approximating polynomial from block 10 (Fig. 1) of the coefficient memory and frequency switching control

Figures 5 and 6, the subtracting counter 22, the number of installed sections, and the decoder 23 control signals q.

The clock frequency P. from the output of the clock frequency generator 19 is fed to the input of the counter 20, the code output of which is connected to the input of the decoder 21. In the decoder 21, a sequence of signals Q {is generated, which enters the high-frequency level meter circuit, as well as to the inputs of the detracting counter of the number of installed sections 22 and a decoder 23.

The subtractive counter 22 at the end of the polling cycle of the multisectional 5 sensor T (4) is loaded with a code of the number of sensor sections and the high-hour5 level gauge goes to the next polling cycle of another section sensor

From the output of the subtracting counter 22, signals are taken that carry information about the number of the polled section. On the basis of these data, as well as the output signals of the decoder 23, a sequence of control signals Q is recorded.

The selection of codes NQ, proportional to the coefficients of the approximating polynomial (3), is carried out by the signals. The codes are written to the reversible counters 11 and 12 at the moments of arrival cj ,. and correspondingly . At the moments of writing codes to counters, the supply of pulse sequences to their counting inputs is prohibited.

During the first clock cycle from the memory block 10 (Fig. 1), the code 11 is recorded through the reversible counter 11 and the PC 12, and the trigger 13, with the arrival of the pulse cj, is set to one. ;

During the first clock cycle, the Nq code is written from PC 12 by the frequency pulses fgn and fQ, arriving at its subtracting and summing inputs through the switching circuit b from block 2 of the frequency memory and primary sensor 1 until resetting PC 12. Here fjjn f 2. At the output trigger 13, the time interval T is formed, the duration of the MS ("

 o2-12

which is filled with pulses of the hour: that fp-jn f, IncomingJ through. switching circuit 5 from the output of the frequency memory block 2 and the primary sensor to the inputs of logical circuits 8 and 9. At the same time, the number of pulse codes are formed at their outputs. and n 1g, which are fed to the summing and subtracting inputs of PC 11, respectively. In PC 11, a sum is generated.

((

considering (5)

f-f

 o.b ..

 (Y

At the beginning of the second clock cycle, the code is rewritten from PC 11 to PC.12, from which it is written off by frequency pulses f before zeroing PC 12. At 60 the trigger 13, an interval is formed which is filled in circuit 5 with frequency pulses f2. The ria output of circuit 5 is formed by the number of pulses which is 65

written to PC 11, forming in it

code .

f

   % 2 - 1PC1-C8).

At the beginning of the third clock cycle, the N2PC-I is rewritten to PC 12, the avRSI code is set to NOIot and, similarly to the previous clock cycle, to PC 11, the code is generated

 f..Cl, A.N

-t-n. (9)

N

ZRS1 -2Vf 2PC1 a

in the fourth, fifth, and sixth cycles, similarly to the first three cycles, codes are generated in PC 11, respectively

 -one

0-t

(ten)

f,

07

, - (

Taking into account the successive substitutions (7) in (.8), (.8) in (9), (9) in SUC (10) „in U1) and U1) in (12), expression (12) takes the form

"VKfe - v

 f

I

ot-fi f;

+ N “

"

, 2

The resulting code of the Mc level (ci2Z- -c () xZ +: c (Q, formed in PC 11 at the end of the sixth cycle, corresponds to the value of the level in the polled section.

The first section is polled twice in one sensor polling cycle. During the first interrogation, the output of the circuit 15 forms a signal fllti), on the basis of which frequency 2 is switched for the first section to the input of the computational converter.

At the end of the second survey of the first section, the generated code of the level arrives at the scheme 16 for the sign of over-, completion. Esl NH. 7 /, then at the moment of arrival of the clock pulse q, the signal V-, 1 is processed (at the same time, ZSLGR. Which increases the state of the counter 17 of the filled sections by one.

If 0 Nf ,,, o scheme 16, the sign of overflow produces an I-zagr load signal. 1 and registers 18 and 14 will be loaded so-. This means that neither the counter 17 of the filled sections and the code of the level of the current section Cz (13), respectively. The polling cycle in the second section is similar to the previous one, and so on. If a; for example, the number of filled sections is four, then the number 4 is recorded in the count 17 of the filled sections, and when polling the fifth section a level code Nf is formed and the number N of the PC 1 and counter 17 are written to the level 14 register 14 and the register of 18 sections Nots ,, ,,. and the level inside the current section of the NI. Upon further polling of already empty sections, the V3arp signals. and the states of registers 14 and 18 change only in the next sensor polling cycle. The process of generating a result in each cycle is similar to that discussed above. Formed result, the result of N N can be transmitted to the display device. The developed high-frequency level gauge has a higher accuracy in measuring low levels. Thus, in the prototype, the error in measuring the levels close to zero for a specific sensor, taking into account the error of the compensation algorithm, is about 10%. The proposed high frequency level gauge has an error in measuring levels (under similar conditions) close to zero, equal to 2%.

l

//

ffotf i / ue / ta

Cffffftftf

/ j

Claims (1)

AUTOMATIC LEVEL LEVEL No. 900120, characterized in that, in order to improve the measurement accuracy in the low-level region, c. it introduced a series-connected dummy frequency generation circuit and an additional switch, connected between the input of the frequency generation circuit and the inputs of the two main switches, and a circuit of the level of the correction circuit connected by one input to the input of the overflow sign circuit, the other input to the control signal generation circuit, and output - to an additional switch, also connected to the sensor output. „.SU.„ 1008621